• Eric Dumazet's avatar
    tcp/dccp: fix other lockdep splats accessing ireq_opt · 06f877d6
    Eric Dumazet authored
    In my first attempt to fix the lockdep splat, I forgot we could
    enter inet_csk_route_req() with a freshly allocated request socket,
    for which refcount has not yet been elevated, due to complex
    SLAB_TYPESAFE_BY_RCU rules.
    
    We either are in rcu_read_lock() section _or_ we own a refcount on the
    request.
    
    Correct RCU verb to use here is rcu_dereference_check(), although it is
    not possible to prove we actually own a reference on a shared
    refcount :/
    
    In v2, I added ireq_opt_deref() helper and use in three places, to fix other
    possible splats.
    
    [   49.844590]  lockdep_rcu_suspicious+0xea/0xf3
    [   49.846487]  inet_csk_route_req+0x53/0x14d
    [   49.848334]  tcp_v4_route_req+0xe/0x10
    [   49.850174]  tcp_conn_request+0x31c/0x6a0
    [   49.851992]  ? __lock_acquire+0x614/0x822
    [   49.854015]  tcp_v4_conn_request+0x5a/0x79
    [   49.855957]  ? tcp_v4_conn_request+0x5a/0x79
    [   49.858052]  tcp_rcv_state_process+0x98/0xdcc
    [   49.859990]  ? sk_filter_trim_cap+0x2f6/0x307
    [   49.862085]  tcp_v4_do_rcv+0xfc/0x145
    [   49.864055]  ? tcp_v4_do_rcv+0xfc/0x145
    [   49.866173]  tcp_v4_rcv+0x5ab/0xaf9
    [   49.868029]  ip_local_deliver_finish+0x1af/0x2e7
    [   49.870064]  ip_local_deliver+0x1b2/0x1c5
    [   49.871775]  ? inet_del_offload+0x45/0x45
    [   49.873916]  ip_rcv_finish+0x3f7/0x471
    [   49.875476]  ip_rcv+0x3f1/0x42f
    [   49.876991]  ? ip_local_deliver_finish+0x2e7/0x2e7
    [   49.878791]  __netif_receive_skb_core+0x6d3/0x950
    [   49.880701]  ? process_backlog+0x7e/0x216
    [   49.882589]  __netif_receive_skb+0x1d/0x5e
    [   49.884122]  process_backlog+0x10c/0x216
    [   49.885812]  net_rx_action+0x147/0x3df
    
    Fixes: a6ca7abe ("tcp/dccp: fix lockdep splat in inet_csk_route_req()")
    Fixes: c92e8c02 ("tcp/dccp: fix ireq->opt races")
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Reported-by: default avatarkernel test robot <fengguang.wu@intel.com>
    Reported-by: default avatarMaciej Żenczykowski <maze@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    06f877d6
tcp_ipv4.c 63.6 KB